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 Class D Switching Power Amplifiers and Power D/A conversion

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 20th September 2017, 01:39 AM #151 SanjeevM diyAudio Member   Join Date: Jun 2017 You're right. I am waiting for the new caps to come. Planning to build a 60000 uf bank. I will have to find a soft start circuit too. BTW any idea how it works?
emedia4u
diyAudio Member

Join Date: Nov 2009
Quote:
 Originally Posted by SanjeevM BTW any idea how it works?
It should be slow charge and fast discharge connected to RESET.
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 Reset.png (11.8 KB, 114 views)

 20th September 2017, 04:08 PM #153 doctormord   diyAudio Member     Join Date: Oct 2007 That wont help the transformer at all. Suitable Inrush-Current-Limiter. PVDD: 38V VAC: 120V VDC_hv_virtual: VAC*1,414 ~170V CBulk: 6000uF + 2x2200uF (EVM) ~ 10000uF Esec = (C*PVDD^2)/2 = (0.01F * 38^2V^2)/2 = 7.22J CBulk_hc_virt = (Esec*2)/VDC_hv_virtual^2 = (7.22J*2)/170^2V^2 = 500uF (@170Vdc) Lets assume 600W maximum system power and 90% efficiency for the transformer. 600W/120VAC * 0.9 = 4.5A For 3A maximum allowable input current (primary) we have: R = VDC_hv_virtual / I = 170V/3A = 57R Inrush current limiter needed: R = 56R E = 7.2J I = 4.5A IRC choosen: SL22 50004 Source: Inrush Current Calculators and How to Select an Inrush Current Limiter Use in series with primary. __________________ 360customs.de - stromrichter.org - Projects: MAX9709 TPA3132D2 TPA3255 TPA3251 - SigmaDSP - CSR8645 - BQ24450 Last edited by doctormord; 20th September 2017 at 04:15 PM.
 Yesterday, 01:03 AM #154 SanjeevM diyAudio Member   Join Date: Jun 2017 I am planning to use this Soft start board:: EA - Transformer Soft Start, EATSS01 – Eight Audio(R) The module adds resistors during startup in the AC path to limit inrush current. (That''s what the rep said!). Last edited by SanjeevM; Yesterday at 01:06 AM.
 Yesterday, 10:31 AM #155 impuls60   diyAudio Member   Join Date: Apr 2011 Looks similar in function to what I ordered 220V 1000W Transformer Delay Power Soft Start Protection Board for Amplifier AMP | eBay. I plan to swith out the series resistors with a 60ohm power resistor. I wonder at what state of charge on the cap bank the soft start board should bybass the resistor?
 Yesterday, 01:14 PM #156 SanjeevM diyAudio Member   Join Date: Jun 2017 The resistors are meant to arrest the sudden inrush caused by caps with zero charge. Perhaps the switchover is just time dependent, lets say changing over after one second, which is enough to pre charge the cap bank. I have an old Yamaha HT. On power on, the relay clicks after a second.
 Yesterday, 01:16 PM #157 SanjeevM diyAudio Member   Join Date: Jun 2017 Since this circuit is connected to the primary side of the trafo, it will not see the capacitor bank.
 Yesterday, 03:54 PM #158 impuls60   diyAudio Member   Join Date: Apr 2011 It's only time dependant yes, see description on mine. Some early internett calculations points me towards 7-8 seconds to fully charge 360 000uF@ 50V with less than 5A at the 230V side.. So if you could bypass at about 6s@80%charged that would be less annoying. I don't have any experince with this so any input would be great!

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